1. Field of the Invention
The present invention relates to a liquid crystal display device which integrally houses a liquid crystal display panel and a backlight which constitutes an illumination light source and is formed on a back side of the panel in a metal frame, and more particularly to a liquid crystal display device which can expand an effective display region, can reduce the thickness and the weight thereof, and can enhance the luminance by effectively utilizing an illumination light of the backlight.
2. Description of the Related Art
A liquid crystal display device forms an electronic latent image on a liquid crystal display panel and visualizes the electronic latent image by irradiating an illumination light. There have been known a liquid crystal display device which utilizes an external light as the illumination light and a liquid crystal display device which incorporates an illumination light source which irradiates light to a back surface or a front surface of the liquid crystal display panel. With respect to a liquid crystal display device which is utilized as display means of a portable electronic terminal such as a portable phone set, a liquid crystal display device which is usually known as a reflective type and uses an external light has been popularly used to achieve the reduction of weight and power consumption. However, because of a demand for a color display and the enhancement of image quality in recent years, a liquid crystal display device which incorporates an illumination light source in a liquid crystal display panel has been popularly used.
With respect to this type of illumination light source, a front light type light source which installs a light source at a front-surface side of a liquid crystal display panel and a backlight type light source which installs a light source on a back side of the liquid crystal display panel have been adopted as a main stream. Particularly, in a liquid crystal display device which uses a color liquid crystal display panel of an active matrix type, a backlight which can easily provide a uniform illumination over a whole surface of a display region thereof and can obtain an illumination light of high luminance has been popularly adopted.
Among various types of backlights, there have been a direct type which installs a light source right below a back surface of a liquid crystal display panel and a side edge type which laminates a light guide plate on a back side of a liquid crystal display panel and installs a light source such as linear lamps or light emitting diodes at end peripheries of the light guide plate. Particularly, with respect to an electronic terminal having a small screen, a liquid crystal display device which adopts the side edge type backlight has been popularly adopted for reducing the thickness and the weight thereof. In the backlight type liquid crystal display device using such a light guide plate, the liquid crystal display panel and the light guide plate have been integrally housed in a laminated manner in a metal frame.
In performing the housing operation, to fix the liquid crystal display, to protect the liquid crystal display from an external impact, and to prevent the lowering of the luminance ratio of the backlight, the liquid crystal display panel and the light guide plate are once housed in a resin-made frame-like mold (resin mold) and then the resin mold is fitted into the metal frame. Accordingly, an effective display region of the liquid crystal display panel is limited by an inner periphery of the resin mold. Further, to prevent a phenomenon that light which propagates in the inside of the light guide plate leaks from end peripheries of the light guide plate thus reducing a quantity of light irradiated to a liquid crystal display panel side, reflection tapes are adhered to the end peripheries of the light guide plate or reflection materials are applied to the end peripheries of the light guide plate. As the prior art which protects the liquid crystal display panel from an external impact, there have been known techniques disclosed in Japanese Laid-open Patent 283560/1995, Japanese Laid-open Patent 286623/1996 and Japanese Laid-open Patent 5722/1997.
In general, the resin mold is an injection molded product and hence, at least a minimum wall thickness of approximately 0.5 mm is necessary at a side wall portion and at a bottom wall portion of the resin mold in view of the restriction imposed by molding conditions. Further, a fixing mechanism for fixing the metal frame and the resin mold is also necessary. This pushes up a manufacturing cost of a mold for forming a resin mold or brings about the lowering of yield factor when the fixing mechanism ruptures at the time of assembling. Further, in the liquid crystal display device which adheres the reflection tapes to the end peripheries of the light guide plate or applies the reflection materials to the end peripheries of the light guide plate, the manufacturing steps become cumbersome. These constitute obstacles which hamper the enlargement of the effective display region and the reduction of thickness and weight of the liquid crystal display device.
In view of the above, it may be possible to propose an idea to directly house the liquid crystal display panel and the light guide plate in the inside of the metal frame without using the resin mold. However, since a substrate of the liquid crystal display panel is usually constituted of a glass material, a buffer structure is necessary between the substrate and the metal frame. Further, when the adhesion of the reflection tapes or the applying of the reflection materials to the end peripheries of the light guide plate is omitted, a quantity of light which is irradiated is reduced.
Accordingly, it is an object of the present invention to provide a liquid crystal display device which can enlarge an effective display region and can reduce a thickness and a weight thereof without using a resin mold and without applying reflection tapes or reflection materials to end peripheries of a light guide plate by adhesion or coating thus preventing the lowering of a quantity of irradiating light.
According to the present invention, a thin-wall spacer having resiliency is integrally formed on an inside of a metal frame and a liquid crystal display panel is fixed to the metal frame by utilizing the resiliency of the spacer. Further, the spacer is formed of a resin material having high reflectance so that light from a light guide plate is effectively utilized whereby the lowering of luminance is obviated.
Due to such a constitution, it is possible to reduce the thickness and the weight of a whole liquid crystal display device and, at the same time, to attenuate an external impact transmitted from the metal frame to the liquid crystal display panel and the light guide plate. Further, the removal of the liquid crystal display panel can be prevented by forming the spacer into a given shape or setting physical characteristics of the spacer to given values. Still further, by molding the spacer using a resin material having high reflectance, it is possible to effectively utilize light from the light guide plate thus obviating the lowering of luminance.